1. Field of the Invention
This invention relates to an information processing system which transmits data between devices thereof in one-to-one communication via a system bus and, in particular, to a simultaneous receiving unit in a data receiving device included in the information system.
2. Description of the Related Art
In an information system, such as a computer system or network, which can display video data streams on a monitor or a display device, the data streams are at first transmitted from a video source device via a system bus and stored in a system memory in the system, when the data streams are displayed on the monitor. Such a process of storing the data streams into the system memory is generally referred to as xe2x80x9ccapturexe2x80x9d.
Next, the stored data streams are sent to a graphic accelerator from the system memory via the system bus. The process is generally referred to as xe2x80x9cplaybackxe2x80x9d. Then, the graphic accelerator sends the data stream to the monitor using a frame buffer, and the data streams are displayed on the monitor as a dynamic or moving image.
Therefore, the data streams are transmitted in the system through the system bus twice and CPU power is consumed at each transmission. This may result not only in a reduction of a data transmission rate as a whole but also in an increase of a load.
Practically, similar problems also take place during network communication. For example, let the same messages be sent to different destinations through the network. In this case, a bandwidth of the network is repeatedly used a plurality of times which are equal to the number of the destinations. In addition, CPU power is wasted at every transmission of the message.
In a communication network, a broadcast communication method is adopted to solve the problems and makes it possible to use the bandwidth of the network only once and to thereby reduce a load of the CPU.
The broadcast communication methods are disclosed in Japanese Laid-Open Publication Nos. H5-324545 (namely, 324545/1993) and S64-62759 (namely, 62759/1989). The methods disclosed in the publications realize broadcast communication by giving group addresses to receiving device groups each of which includes a plurality of data receiving devices and by designating the group addresses at the beginning of data communication.
The broadcast communication methods are also disclosed in Japanese Laid-Open Publication Nos. S63-215238 (namely, 215238/1988) and H3-187628 (namely, 187628/1991), H3-245636 (namely, 245636/1991), and H7-074745 (namely, 074745/1995). Among these publications, S63-215238 discloses the method in which a plurality of receiving devices receive, through a network, a packet having an address, the receiving devices determine an address of the packet. In this event, data in the packet are received and fetched only by the receiving device which has the address matched with the address of the packet. However, no consideration is made at all about application of such broadcast communication methods to a display of video images.
Therefore, it is an object of the invention to provide a system which can avoid a waste of resources in a network and which can also save power consumption.
It is another object of the invention to provide a system which can realize power consumption by parallel reception of video data signals.
According to an embodiment of the invention, a system in which data communication is performed between devices via a bus comprising a data sending device which sends data via the bus in one-to-one data communication, a first data receiving device which receives the data from the data sending device via the bus, and at least one second data receiving device which receives the data sent from the data sending device to the first data receiving device, simultaneously with the receiving by the first receiving device.